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Table 2 Sample size calculation for follow-up component

From: An approach for evaluating early and long term mother-to-child transmission of HIV (MTCT) in low and middle income countries: a South African experience

  1. Footnote: The bolded boxes highlight the sample sizes selected to estimate HIV infection or death (green box) or 18-month MTCT only (red box), with 30% precision, a design effect of 2 and assuming 20 or 30% loss to follow-up. These show that assuming a design effect of 2, 18-month MTCT of 5% (3.5–6.5%) and 10% (7–13%) MTCT or death, 1620 infants are needed to estimate MTCT and 768 infants are needed to estimate HIV or death. Assuming 30% loss to follow-up, 2314 infants need to be enrolled to estimate MTCT and HIV-free survival. Sample size calculations were made using standard nQuery Version 4.0